1. Field of the Invention
The present invention relates to a branch pipe liner bag for lining an inner wall of a branch pipe which becomes too old to perform properly and a pipe lining method which may be implemented using the branch pipe liner bag and a main pipe liner bag.
2. Description of the Related Art
When a pipe-line laid underground such as a sewage pipe or the like becomes defective or too old to perform properly, the pipe is repaired and rehabilitated employing a pipe lining method for lining the inner wall thereof without being dug out from the underground. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering.
The pipe lining method utilizes a pipe liner bag made of a flexible resin-absorbent material, having the outer surface thereof covered with a highly air-tight film, impregnated with an unhardened liquid hardenable resin. The pipe liner bag is turned inside out to be inserted deeper into the pipe-line (this manner of insertion shall be called "everting" hereafter) by pressurized fluid, and then the pipe liner bag is pressed against the inner peripheral surface of the pipe-line, and while the state remains, the pipe liner bag is heated or otherwise processed to harden the hardenable resin impregnated therein, thereby lining the inner peripheral surface of the pipe-line with the hardened pipe liner bag, thus repairing the pipe-line.
By the way, the pipe lining method described above can be applicable similarly to a branch pipe of a sewage pipe and the like joining a main pipe thereof, but the inventors of the present invention have proposed a branch pipe lining method for lining the branch pipe using a branch pipe liner bag having a flange formed at one end thereof. In the branch pipe lining method, while a flange of a branch pipe liner bag is bonded to the circumference of a branch pipe opening of a main pipe, the branch pipe liner bag is everted (i.e. turned inside out) into the branch pipe from the main pipe toward the ground surface by pressurized fluid to be bonded to the inner wall of the branch pipe, and while the state is being kept, the branch pipe liner bag is heated or otherwise processed to have a hardenable resin impregnated therein hardened.
Therefore, if a main pipe is lined with a main pipe liner bag by the above-described method after a branch pipe is lined by the above-described branch pipe lining method, an opening of the branch pipe to the main pipe (a branch pipe opening) is blocked by the main pipe liner bag, thereby requiring a boring work to be done for the main pipe liner bag blocking the branch pipe opening.
As a main pipe of a size in a diameter of 800 m/m or less is too narrow for a man to enter, it is necessary to operate by remote operation from the ground surface a piercing robot introduced into the main pipe to drive a cutter for piercing the main pipe liner bag blocking the branch pipe opening.
However, piercing the main pipe liner bag by remotely operating the piercing robot requires expertise and skill, and a flange and other portions of the branch pipe liner bag may be damaged by the cutter, thereby causing a problem such as infiltration of the underground water into the main pipe from the damaged portions. More specifically, depending on how the branch pipe is connected with the main pipe, damage of the branch pipe liner bag may be unavoidable.